In recent years, bandwidths for data communication systems have continuously increased to provide improved system performance. Indeed, the bandwidths of address and data busses can be 128 bits or more. With the increase in the bandwidths of address and data busses, however, interference such as crosstalk has become a serious problem.
In a semiconductor IC, bus lines of a bus (e.g., data bus, address bus) are arranged in an order from a least significant bit (LSB) to a most significant bit (MSB), and intervals (spacing) between the bus lines are preferably set to prevent interference such as crosstalk. Since the interference increases proportionally to the increase in the width of a bus, the interval between the bus lines should be increased to prevent crosstalk interference. However, an increase in the intervals results in an increase in the chip area of the semiconductor IC, which is undesirable. Therefore, there is a strong need for a methods and circuits for driving data and address busses, which are capable of reducing interference such as crosstalk, even when the width of a bus increases.
FIG. 1 is a timing diagram illustrating a conventional bus driving method and FIG. 2 illustrates a conventional driving circuit which can be used for implementing the method of FIG. 1. For convenience of explanation, FIGS. 1 and 2 illustrate a conventional bus driving method and circuit for an 8-bit data bus.
Referring to FIGS. 1 and 2, in response to activation of an enable signal (EN), drivers 21-23 receive data D0--D7 and simultaneously drive data buses (DATA[7:0]). Assuming the intervals among data buses in the semiconductor IC chip are narrow and DATA[7:0] is ‘01000101’, victim DATA6 is exposed to a −4C coupling effect (i.e., a type of interference) by aggressors DATA7 and DATA5 such that the logic value “1” of DATA6 may drop below an output high voltage (Voh). Further, when exposed to a +4C coupling effect by aggressors DATA2 and DATA0, the logic value “0” of the victim DATA1 may rise above an output low voltage (Vol). In these cases, the operation speed of the semiconductor IC may decrease or erroneous operations may occur.
More specifically, the term “coupling” means that transition of DATA[i] affects DATA[i+1], wherein DATA[i] which produces the effect is referred to as an “aggressor”, and wherein DATA[i+1] which is affected is referred to as a “victim.” Capacitance between the aggressor and the victim is referred to as coupling capacitance (C).
As described above, with the conventional bus driving method and circuit, bus lines of the bus are simultaneously driven such that when the width of the bus increases, interference may result, which can cause the loss of operating speed of the semiconductor IC and/or cause erroneous operations to occur.